How does the type of surface affect the amount of
heat absorbed or radiated?

Question Date: 2013-04-03

Answer 1:

Surfaces which are reflective absorb less heat
because the incoming energy is reflected away. It
also turns out that the same is true for heat
leaving an object - reflective surfaces try to
emit heat but it tends to get reflected back
inside the object so it gives off less heat. So
non-shiny black surfaces, like asphalt for
example, will both absorb more heat, and give off
more heat. This is why the spectrum of
electromagnetic radiation given off by a heated
object is called "black body radiation", because a
perfectly black body will absorb and emit the most
electromagnetic radiation

.

Answer 2:

When you talk about heat, it can be
transported in three different ways:
- Conduction: molecules crashing into each
other, passing heat from a warm area to a colder
area directly through a material
- Convection: molecules carrying the energy
through a liquid or gas
- Radiation: heat being transferred by
electromagnetic radiation (light)

If two surfaces are in contact with each other,
the contact between the two will help determine
the ability for heat to transfer through
conduction. Rougher surfaces will likely have
less contact and transfer heat less effectively.
Convection should not be affected much by this.
If a surface is particularly rough or smooth,
this may affect how much radiative heat it can
absorb as well, but this is complicated, and
depends on the size scale of the roughness. The
type of material (glass, metal, plastic, etc)
will also affect each of these.